beta

beta

[ba´tah]

second letter of the Greek alphabet, β; used to denote the second position in a classification system. Often used in names of chemical compounds to distinguish one of two or more isomers or to indicate the position of substituent atoms or groups in certain compounds. Also used to distinguish types of radioactive decay; brain rhythms or waves; adrenergic receptors; secretory cells of the various organs of the body that stain with basic dyes, such as the beta cells of the pancreas; and the type of hemolytic streptococci that produce a zone of decolorization when grown on blood media.

beta-adrenergic blocking agent (beta-blocker) any of a group of drugs that block the action of epinephrine at beta-adrenergic receptors on cells of effector organs. There are two types of these receptors: β1-receptors in the myocardium and β2-receptors in the bronchial and vascular smooth muscles. The principal effects of beta-adrenergic stimulation are increased heart rate and contractility, vasodilation of the arterioles that supply the skeletal muscles, and relaxation of bronchial muscles.

Because of their effects on the heart, these agents are used to treat angina pectoris, hypertension, and cardiac arrhythmias. And, because they decrease the workload of the heart, they are effective in reducing the long-term risk of mortality and reinfarction after recovery from the acute phase of a myocardial infarction. They are an important adjunct in treatment of heart failure and are also used for prophylaxis of migraine.

Nonselective beta-adrenergic blocking agents affect both types of receptors and can produce bronchospasm in patients with asthma or chronic obstructive pulmonary disease. If such patients need one of these drugs, they should be given a cardioselective one that preferentially blocks the β1-receptors in the heart.

Nonselective agents include propranolol (Inderal), used for treatment of angina, hypertension, arrhythmias, and migraine and for prophylaxis after the acute phase of a myocardial infarction; nadolol (Corgard), used for treatment of angina and hypertension; and timolol, used as an ophthalmic preparation (Timoptic) for treatment of glaucoma and as an oral preparation (Blocadren) for treatment of hypertension and for prophylaxis after the acute phase of a myocardial infarction. Cardioselective beta-adrenergic blocking agents are used for treatment of hypertension and include atenolol (Tenormin) and metoprolol (Lopressor).

beta particles negatively charged particles emitted by radioactive elements, the result of disintegration of neutrons; their source is the unstable atoms of radioactive metals such as radium and uranium. There are three general types of emissions from radioactive substances: alpha and beta particles and gamma rays. Beta particles are less penetrating than gamma rays and may be used to treat certain conditions on or near the surface of the body. See also radiation and radiation therapy.

β

In typography, do not substitute the German compound letter β for this Greek letter.

1. Second letter of the Greek alphabet, beta.

2. chemistry denotes the second in a series, the second carbon from a functional (for example, carboxylic) group, or the direction of a chemical bond toward the viewer. For terms having this prefix, see the specific term.

3. Pressure coefficient.

be·ta (β),

(bā'tă), In typography, do not substitute the German compound letter β for the Greek letter β.

Second letter of the Greek alphabet, β (see entry at start of letter "Bs.")

[G.]

β

/β/ (beta, the second letter of the Greek alphabet) β chain of hemoglobin.

beta

/be·ta/ (ba´tah) β, the second letter of the Greek alphabet; see also β-.

beta

[bē′tə, bā′tə]

B, β, the second letter of the Greek alphabet, used in scientific notation to denote position of a carbon atom in a molecule, a type of protein configuration, or identification of a type of activity, as beta blocker, beta particle, or beta rhythm. It is used in statistics to define an error in the interpretation of study results.

beta

MedspeakThe second letter in the Greek alphabet. The term is included here to flag the differences in pronunciation between British and American English. Medspeak-UK: pronounced, BEE tuh.Medspeak-US: pronounced, BAY tuh.

StatisticsThe probability of a Type-II false-negative error. In hypothesis testing, beta is the probability of concluding incorrectly that an intervention is not effective when it has true effect. 1-b is the power to detect an effect of an intervention if one truly exists

beta

β The second letter of the Greek alphabet; Statistics The probability of a Type II–false-negative error. See Type II error. Cf Alpha.

β

Abbreviation for beta.

be·ta

(β) (bā'tă)

1. Second letter of the Greek alphabet.

2. chemistry Denotes the second in a series, the second carbon from a functional (e.g., carboxylic) group, or the direction of a chemical bond toward the viewer. For terms with the prefix β, see the specific term.

beta

The second letter of the Greek alphabet, often used to denote the order in a sequence.

beta (bāˑ·t),

Beta

a genus of the Polygonaceae family.

Beta vulgaris

this species includes the large fodder roots. They provide a massive source of feed energy but they can cause poisoning if used unintelligently, e.g. (1) carbohydrate engorgement and lactic acidosis if too many are fed; (2) partly cooked mangels grown on high nitrate soils may cause primary nitrite poisoning; (3) the tops may contain toxic amounts of oxalate; (4) a sole diet of beet pulp is thought to cause a nutritional deficiency of vitamin A in cattle leading to blindness and encephalopathy. Called also fodder beet, sugar beet, mangels, mangolds, mangel-wurzel, beetroot.

beta

the second letter of the Greek alphabet, B or β; used to denote the second position in a chemical classification system. Often used in names of chemical compounds to distinguish one of two or more isomers or to indicate the position of substituent atoms or groups in certain compounds. Also used to distinguish types of radioactive decay; brain rhythms or waves; adrenergic receptors; secretory cells of the various organs of the body that stain with basic dyes, such as the beta cells of the pancreas; and the type of hemolysis induced by bacteria that results in a zone of complete hemolysis when grown on blood agar, except for staphylococci.

β-adrenergic receptors specific sites on effector cells that respond to epinephrine. There are two types: β1-receptors, found in the heart and small intestine, and β2-receptors, found in the bronchi, blood vessels and uterus.

a form of secondary structure of a polypeptide in which β strands of amino acids are wound into a super secondary structure; usually interconnected by α helical regions of the polypeptide on the outside of the molecule.

beta-blocker

a drug that blocks the action of epinephrine at beta-adrenergic receptors on cells of effector organs. There are two types of these receptors: β1-receptors in the myocardium and β2-receptors in the bronchial and vascular smooth muscles. The principal effects of beta-adrenergic stimulation are increased heart rate and contractility, vasodilation of the arterioles that supply the skeletal muscles, and relaxation of bronchial muscles.

beta brain waves

those having a frequency of more than 10 hertz (pulsations per second); seen during wakefulness. See also electroencephalography.

a common structural feature of many proteins in which the single polypeptide chain is folded back and forth upon itself with each folded section running in an opposite direction to its nearest neighbors. The folded sections are held together by hydrogen bonds and the arrangement which occurs, particularly in the core of proteins, confers great stability on the molecule.

beta subunit

second-named chain (or subunit) occurring in the functional organization of macromolecules, usually proteins, containing two or more chains.

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